What is the difference between latitude and longitude lines on a sectional chart?

Latitude lines, also called parallels, run east and west across the chart and measure distance north or south of the equator in degrees. Longitude lines, called meridians, run north and south and measure distance east or west of the Prime Meridian. Together they form a grid system that allows pilots to pinpoint any location on Earth to a precise coordinate, which is essential for reporting positions and identifying airspace boundaries under 14 CFR Part 107.

How do you read latitude and longitude coordinates on a sectional chart?

On a sectional chart, latitude is read first and expressed in degrees, minutes, and seconds north or south of the equator, while longitude follows and is expressed in degrees, minutes, and seconds east or west of the Prime Meridian. The tick marks along the chart borders subdivide each degree into minutes to help you interpolate precise locations between printed grid lines. As described in the Pilot's Handbook of Aeronautical Knowledge, practicing this skill allows remote pilots to accurately describe their operating location and verify compliance with airspace restrictions.

Why do remote pilots need to understand latitude and longitude on sectional charts?

Under 14 CFR Part 107, remote pilots must operate within specific geographic boundaries, avoid controlled and restricted airspace, and be able to accurately report their location when required. Latitude and longitude coordinates are the standard reference system used by air traffic control, LAANC authorizations, and aeronautical charts to define those boundaries precisely. Without the ability to read and apply this coordinate grid, a remote pilot cannot reliably confirm that a planned operation complies with FAA airspace requirements.

Latitude and Longitude Grid Lines on Sectional Charts

Every sectional aeronautical chart is criss-crossed by a network of blue grid lines running east-west and north-south. These are the lines of latitude and longitude — the foundation of the geographic coordinate system used worldwide in aviation, navigation, and mapping. For a Part 107 remote pilot, understanding how to read and use these lines is not just an academic exercise. It is a practical skill you will rely on every time you verify airspace boundaries, calculate a position for a waiver application, or communicate your operating location to air traffic control or other authorities.

This article explains how latitude and longitude work, how they appear on FAA sectional charts, and why mastering the grid is essential for safe and legal small UAS (sUAS) operations under 14 CFR Part 107.

How the Coordinate System Works

Latitude measures how far north or south a point is from the equator. The equator is defined as 0° latitude, the North Pole is 90° North (90°N), and the South Pole is 90° South (90°S). Lines of latitude are sometimes called parallels because every line of latitude runs parallel to the equator and to every other line of latitude — they never converge or intersect.

Longitude measures how far east or west a point is from the prime meridian, an arbitrary line that passes through Greenwich, England, established by international agreement. Longitude ranges from 0° at the prime meridian to 180° East and 180° West, meeting at the International Date Line in the Pacific. Lines of longitude are called meridians. Unlike parallels, meridians are not parallel to each other — they converge at both poles, meaning the east-west distance represented by one degree of longitude shrinks as you move away from the equator toward the poles.

Degrees, Minutes, and Seconds

Each degree (°) of arc is subdivided into 60 minutes ('), and each minute is further divided into 60 seconds (″). This system allows very precise location descriptions. On a sectional chart, you will typically see tick marks and labels at every 30-minute interval (half a degree) for both latitude and longitude, with the full-degree values clearly annotated. Some newer digital and paper charts also show tick marks at smaller intervals. In the continental United States, latitude values generally run from about 24°N in the Florida Keys to about 49°N along the Canadian border, and longitude values run from about 67°W along the Maine coast to about 124°W on the Pacific coast of the Pacific Northwest.

When recording a coordinate for operational planning or a LAANC request, remote pilots often express positions in decimal degrees (for example, 38.8977°N, 77.0365°W) rather than in degrees-minutes-seconds, because most smartphone apps and flight-planning software use that format. Either format is mathematically equivalent, but you should know how to convert: decimal minutes are divided by 60 to get the decimal fraction of a degree.

How Grid Lines Appear on a Sectional Chart

On a paper sectional chart, latitude and longitude lines are printed as thin blue lines forming a rectangular grid. The values are printed in blue numerals along the edges of the chart and, on large charts, repeated at intervals within the chart body so you never have to count too far from a label. Latitude values are printed along the left and right margins; longitude values appear along the top and bottom margins.

At the intersection of every full degree of latitude and longitude, you will find a cross (+) or tick mark that makes the exact degree point easy to spot. Between full-degree lines, tick marks appear at 30-minute intervals along the neat lines (edges) of the chart. Because the continental US spans many degrees of longitude, a single sectional chart might cover only a few degrees in each direction — sectionals are printed at a scale of 1:500,000, meaning one inch on the chart represents approximately 6.86 statute miles (about 5.96 nautical miles) on the ground.

Why Latitude and Longitude Matter for Part 107 Remote Pilots

Under 14 CFR Part 107, a remote pilot in command is responsible for knowing the exact airspace classification of the operating area before every flight. Airspace boundaries on sectional charts are defined geographically — often by latitude and longitude coordinates listed in the Chart Supplement (formerly the Airport/Facility Directory) or in the Federal Register for special-use airspace. Reading the grid accurately is the only reliable way to determine whether a proposed flight location falls inside or outside a particular airspace boundary.

For example, Class D airspace around a small airport might extend 4 nautical miles from the airport reference point and be depicted on the sectional chart as a dashed blue circle. To confirm your drone launch site is outside that circle, you need to estimate distances relative to identifiable latitude and longitude reference points on the chart — or use a digital tool that draws on the same underlying coordinate data.

LAANC (Low Altitude Authorization and Notification Capability) grids are also built entirely on the latitude/longitude system. Each LAANC grid square has precise geographic corners defined by latitude and longitude coordinates. When you submit a flight through a LAANC-enabled app, the app checks your entered GPS coordinates against FAA airspace data that uses the same coordinate system printed on the sectional chart. A remote pilot who understands the grid can catch errors when an app places a pin in the wrong location.

Beyond airspace, latitude and longitude are also used to define Temporary Flight Restrictions (TFRs), special-use airspace (restricted areas, MOAs, prohibited areas), and stadium TFRs. Each of these is described in a NOTAM using geographic coordinates. Being able to mentally reconcile those coordinates with features on a sectional chart is a critical situational awareness skill.

Key Numbers and Rules

1° of latitude = approximately 60 nautical miles anywhere on Earth (since parallels never converge, this value is constant).
1° of longitude = approximately 60 nautical miles at the equator, but that distance decreases as you move toward the poles. At 45°N (roughly the latitude of Minneapolis or Portland, OR), 1° of longitude equals approximately 42 nautical miles.
1 minute of latitude = approximately 1 nautical mile. This is the origin of the nautical mile as a unit — it was originally defined as one arc-minute of latitude along the Earth's surface.
Sectional chart scale: 1:500,000. One inch on the chart = approximately 6.86 statute miles (about 5.96 nautical miles, or approximately 5.96 arc-minutes of latitude).
Grid lines on sectionals are labeled every 30 minutes (0.5°) along chart edges, with full-degree intersections marked inside the chart body.
Latitude is always stated first, longitude second, when writing a coordinate pair (e.g., 33°45'N, 118°24'W).
Northern Hemisphere latitudes are North (N); Western Hemisphere longitudes are West (W) for all US locations.

Reading a Position on a Sectional Chart: Step by Step

Identify the nearest labeled latitude line (a full or half-degree parallel) below your point of interest.
Count the tick marks northward from that line to your point. Each tick represents 30 minutes (if ticks are at half-degree intervals) or the labeled subdivision.
Estimate any remaining fraction of the interval by eye or by using the chart's latitude/longitude scale printed in the legend.
Repeat the process horizontally using longitude lines to the west of your point, counting eastward.
Combine the two values to produce a coordinate pair, and verify against a known landmark (airport symbol, city, etc.) to confirm you have not made an off-by-one error.

Common Test Traps

Confusing latitude and longitude direction. Latitude lines run east-west (horizontally) but measure north-south distance. Longitude lines run north-south (vertically) but measure east-west distance. The FAA knowledge test exploits this confusion regularly.
Assuming 1° of longitude always equals 60 nautical miles. That is only true at the equator. In the continental US, 1° of longitude is significantly shorter than 60 nm — a critical distinction when estimating distances to airspace boundaries.
Reversing the coordinate pair order. Latitude always comes first, then longitude. Writing it backwards will place your position in the wrong hemisphere on any automated system.
Misreading the W (West) longitude values. In the US, longitude numbers increase as you move westward (from about 67°W to 124°W). Moving your finger to the left on the chart means increasing longitude values, which is counterintuitive for some students who expect higher numbers to the right.
Overlooking the difference between arc-minutes and decimal minutes. An app might show 33.75°N, while a chart shows 33°45'N — these are the same point (45 ÷ 60 = 0.75), but students sometimes treat them as different values. Verify conversions before filing any LAANC or waiver request.